Closing a private road, Washington State

Hi all, not sure if the right place but any help is much appreciated. I have taken over control of a family property that has a private road going through it. My property on both sides. Have researched for easements, and there are none. Nobody has ever had permission to use it (have owned 100yrs+). It joins the end of the County road that ends at my driveway with another County road a few miles away. Nobody needs it for access to their property. Have contacted State, County road and Fire Dept. Fire department is all for closing the road, I offered to have approved lock boxes on gates at either end. The State has land that borders me, but can be fully accessed from the other direction. The County is claiming a "historic right" to keep the road open. It states private road on the official map. It is in the middle of a forest with terrible fire risk. There were 2 within a mile last year. I find cigarette butts and other signs of fire along the road, with garbage etc. There are countless vehicles and dirt bikes that fly past, many operated by minors. I'm all for people enjoying the outdoors, but not at the expense of the environment. Please help. Thank you from Washington State.